add support for unlinkat

Author: Mic92

CHANGELOG.md

@@ -24,6 +24,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   ([#739](https://github.com/nix-rust/nix/pull/739))
 - Added nix::sys::ptrace::detach. 
   ([#749](https://github.com/nix-rust/nix/pull/749))
+- Added `nix::unistd::unlinkat`.
+  ([#753](https://github.com/nix-rust/nix/pull/753))
 
 ### Changed
 - Renamed existing `ptrace` wrappers to encourage namespacing ([#692](https://github.com/nix-rust/nix/pull/692))

src/fcntl.rs

@@ -11,10 +11,12 @@ use sys::uio::IoVec;  // For vmsplice
 libc_bitflags!{
     pub struct AtFlags: c_int {
         AT_SYMLINK_NOFOLLOW;
-        #[cfg(any(target_os = "android", target_os = "linux"))]
+        #[cfg(any(target_os = "linux", target_os = "android"))]
+        AT_REMOVEDIR;
+        #[cfg(any(target_os = "linux", target_os = "android"))]
         AT_NO_AUTOMOUNT;
-        #[cfg(any(target_os = "android", target_os = "linux"))]
-        AT_EMPTY_PATH;
+        #[cfg(any(target_os = "linux", target_os = "android"))]
+        AT_EMPTY_PATH
     }
 }
 

src/unistd.rs

@@ -2,7 +2,7 @@
 
 use errno;
 use {Errno, Error, Result, NixPath};
-use fcntl::{fcntl, OFlag, O_CLOEXEC, FD_CLOEXEC};
+use fcntl::{AtFlags, fcntl, OFlag, O_CLOEXEC, FD_CLOEXEC};
 use fcntl::FcntlArg::F_SETFD;
 use libc::{self, c_char, c_void, c_int, c_long, c_uint, size_t, pid_t, off_t,
            uid_t, gid_t, mode_t};
@@ -914,6 +914,17 @@ pub fn unlink<P: ?Sized + NixPath>(path: &P) -> Result<()> {
     Errno::result(res).map(drop)
 }
 
+/// Delete a name and possibly the file it refers to
+/// ([posix specification](http://pubs.opengroup.org/onlinepubs/9699919799/functions/unlinkat.html)).
+pub fn unlinkat<P: ?Sized + NixPath>(fd: RawFd, pathname: &P, flags: AtFlags) -> Result<()> {
+    let res = try!(pathname.with_nix_path(|cstr| {
+        unsafe {
+            libc::unlinkat(fd, cstr.as_ptr(), flags.bits())
+        }
+    }));
+    Errno::result(res).map(drop)
+}
+
 #[inline]
 pub fn chroot<P: ?Sized + NixPath>(path: &P) -> Result<()> {
     let res = try!(path.with_nix_path(|cstr| {

test/test_unistd.rs

@@ -1,5 +1,6 @@
 extern crate tempdir;
 
+use nix::fcntl;
 use nix::unistd::*;
 use nix::unistd::ForkResult::*;
 use nix::sys::wait::*;
@@ -225,6 +226,21 @@ fn test_lseek() {
     close(tmpfd).unwrap();
 }
 
+#[test]
+fn test_unlinkat() {
+    let tempdir = TempDir::new("nix-test_unlinkat").unwrap();
+    let dirfd = fcntl::open(tempdir.path(),
+                            fcntl::OFlag::empty(),
+                            stat::Mode::empty());
+    let file = tempdir.path().join("foo");
+    File::create(&file).unwrap();
+
+    unlinkat(dirfd.unwrap(),
+            &file.file_name(),
+            fcntl::AtFlags::empty()).unwrap();
+    assert!(!file.exists());
+}
+
 #[cfg(any(target_os = "linux", target_os = "android"))]
 #[test]
 fn test_lseek64() {